Generally, a photodynamic therapy is one of the most spotlighted therapies for cancer. According to the photodynamic therapy, once a photosensitizer sensitive to light is put into a human body under light irradiated from outside, abundant oxygen in the human's body and the external light chemically react with each other, thereby producing singlet oxygen or free radical. The singlet oxygen or free radical serve to destroy each kind of disease tissues or cancer cells.
The photodynamic therapy has advantages that only cancer cells can be removed with maintaining normal cells, and local anesthesia can be simply performed with excluding danger from general anesthesia. The photodynamic therapy has been intensively researched since 1980's, and clinical surgeries thereof were approved in 1990's in Canada, Germany, Japan, etc. The photodynamic therapy is being world-widely used as therapy for esophageal cancer was approved in January 1996, and therapy for early lung cancer was approved in September in 1997 by the Food and Drug Administration (FDA).
However, the photodynamic therapy being currently utilized can not be used to voluminous tumor due to limitation of light transmittance, and causes side effects of photo-cytotoxicity since photosensitizer slowly reacts with a human body. Furthermore, since photosensitizer concentration inside tumor is low, therapeutic effectiveness is not enhanced. The photosensitizer may cause side effects by being accumulated in a human body for a long time, rather than serve as a photosensitizer for a therapy. Accordingly, required is a novel photosensitizer capable of reducing side effects by enhancing selection degree for tumor and capable of enhancing therapeutic effectiveness by laser irradiation.
Accordingly, the present inventors have developed a novel photosensitizer that has high selection and accumulation ratio for cancerous tissues, and reduces the conventional photo-cytotoxicity.